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Nervous system - physiology
Nervous system - physiology
104
Anatomy
Undergraduate 2
04/15/2009

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Term
What is membrane potential?
Definition
The electrical difference across the cell membrane
Term
What is the typical value for resting membrane potential?
Definition
-40mV -> -80mV
Term
What are the 3 major ions that are responsible for establishing the resting membrane potential?
Definition
sodium, potassium and chloride
Term
What is the intracellular and extracellular concentration of sodium?
Definition
intracellular = 15mEq/L Extracellular = 145 mEq/L
Term
What is the intracellular and extracellular concentration of potassium?
Definition
intracellular = 135mEq/L Extracellular = 5mEq/L
Term
What is the intracellular and extracellular concentration of Chloride?
Definition
Intracellular = 8mEq/L extracellular = 110mEq/L
Term
What are the relative permeabilities of the three ions of importance?
Definition
sodium = 0.05; potassium = 1.0; Chloride = 0.45
Term
What are the two main factors that contribute to Vm?
Definition
1. magnitude of the concentration gradients of ions 2. permeabilities of the membrane to ions
Term
At resting Vm, which ion has the greatest permeability to the membrane?
Definition
potassium (1.0) then chloride(0.45) then sodium (0.05)
Term
What maintains the concentration gradient needed to establish Vm?
Definition
Sodium/potassium ATPase
Term
What causes the range in values of Vm for different excitable cells?
Definition
Different cells are under different concentrations of ions and different permeabilities
Term
What dictates the movement of ions into and out of the cell?
Definition
The electrochemical gradient
Term
Describe how the electrochemical gradient influences the movement of sodium?
Definition
electrical - positively charged sodium is attracted to negative Vm; Chemical - large concentration gradient for sodium to move into the cell
Term
Describe how the electrochemical gradient influences the movement of potassium?
Definition
Electrical - positively charged K+ is attracted to negative Vm; Chemical - Large concentration gradient for K+ to move OUT of the cell
Term
Describe how the electrochemical gradient influences the movement of Chloride?
Definition
Electrical - Negatively charged Cl- is repulsed by negative Vm; Chemical - large concentration gradient for Cl- to move into the cell
Term
What would be the effect to resting Vm if you increase extracellular Na+?
Definition
Causes Vm to become more positive (depolarization)
Term
What would be the effect to resting Vm if you increase extracellular K+?
Definition
Causes Vm to become more positive (depolarization)
Term
What would be the effect to resting Vm if you increase extracellular Cl-?
Definition
Causes Vm to become more negative (hyperpolarization)
Term
What would be the effect to resting Vm if you Decrease extracellular Na+?
Definition
Causes a hyperpolarization
Term
What would be the effect to resting Vm if you Decrease extracellular K+?
Definition
Causes a hyperpolarization
Term
What would be the effect to resting Vm if you Decrease extracellular Cl-?
Definition
Causes a depolarization
Term
What would be the effect to resting Vm if you increase intracellular Na+?
Definition
Causes a hyperpolarization
Term
What would be the effect to resting Vm if you increase intracellular K+?
Definition
Causes a hyperpolarization
Term
What would be the effect to resting Vm if you increase intracellular Cl-?
Definition
Causes a depolarization
Term
What would be the effect to resting Vm if you decrease intracellular Na+?
Definition
Causes a depolarization
Term
What would be the effect to resting Vm if you increase intracellular K+?
Definition
causes a HYPERpolarization
Term
What would be the effect to resting Vm if you increase intracellular Cl-?
Definition
Causes a DEpolarization
Term
Changing the concentration of which ion will have the greatest effect on Vm?
Definition
Potassium (K+) because it is the most permeable to the membrane
Term
What is an action potential?
Definition
This is an electrical impulse. It is local, very large and very rapid change in Vm. Occurs solely in excitable cells and is caused by the rapid movement of Na+ into the cell and K+ out.
Term
What is threshold?
Definition
Point at which sufficient depolarization of Vm occurs to elicit an action potential (tremendous increase in the permeability of Na+ and K+)
Term
What is the all or none response of an action potential mean?
Definition
If threshold is met; an action potential will always be elicited. If threshold is not met; action potentials will not necessarily be met
Term
Describe what happens during an action potential?
Definition
An excitable cell is stimulated, depolarized and threshold is met. Voltage gated sodium chanels will open and dramatically increase the permeability of Na causing a large rapid increase in Vm. This change in Vm will cause sodium chanels to inactivate (stoping sodium coming in) and also open K+ channels causing a repolarization. Because K+ channels remain open for a period of time, you get an after hyperpolarization and then the cell returns to Vm
Term
What is a refractory period?
Definition
Period of time when a cell fails to respond to a stimulus of threshold intensity
Term
What is the absolute refractory period?
Definition
No action potentials can be elicited during this time; this is due to the fact that sodium channels are inactivated (occurs during the depolarization/repolarization phase)
Term
What is the relative refractory period?
Definition
Possible to elicit an action potential during this period of time. It occurs during the afterhyperpolarization phase. However, a greater stimulus is needed during this time.
Term
What determines the velocity that an action potential is conducted down an axon?
Definition
Fiber diameter (larger fibers are faster) and mylenation (more myelinated is faster)
Term
What is continuous conduction?
Definition
occurs with unmyelinated axons, action potential in one region stimulates an action potential in an adjacent region. Conduction velocity = 2 meters/sec. Unidirectional action potential is ensured by absolute refractory period
Term
What dictates the frequency of action potentials?
Definition
How intense the stimulation is. For example, mild pain will cause low frequency; severe pain will cause very high frequency
Term
What is a synapse and what are the 2 types?
Definition
Junction between two cells that allows communication between those two cells. Two types are 1. electrical and 2. chemical
Term
What is an electrical synapse?
Definition
communication between two cells via gap junctions. These gap junctions are formed by connexins (a 6 subunit pore forming protein)
Term
What is a Chemical synapse?
Definition
Communication between two cells via release of chemicals. There is a pre-synaptic membrane (membrane at the synapse where AP are transmitted from), post-synaptic (membrane at the synapse where AP are transmitted to) and synaptic cleft (small gap between presynaptic and postsynaptic membranes)
Term
What is a neurotransmitter?
Definition
Chemicals that transmit signals from presynaptic to postsynaptic membranes. Most commonly released from synaptic vessicles at synaptic knobs.
Term
How is neurotransmitter released?
Definition
Action potential travels down the synaptic knob of presynaptic membrane. Causes voltage-gated calcium channels to open which increases intracellular calcium and signals for the release of neurotransmitter from synaptic vessicles. Neurotransmitter is released into synaptic cleft and binds to receptors on the post-synaptic membrane. Ions channels open in postsynaptic membrane and transmission continues.
Term
What happens to neurotransmitter after it has been released while it is in the synaptic cleft (what is its fate)?
Definition
it is either taken back up by the presynaptic membrane or astrocytes or it is degrades
Term
What is an EPSP?
Definition
a depolarizing current that could cause the cell to reach threshold but not always
Term
What is an IPSP?
Definition
A hyperpolarizing current
Term
What is summation?
Definition
Integration of EPSP's and IPSP's; determines if there will be a change in Vm to get an action potential
Term
What is temporal summation?
Definition
When multiple postsynaptic potentials from the SAME SYNAPSE converge at about the same time
Term
What is Spatial summation?
Definition
When multiple postsynaptic potentials from DIFFERENT SYNAPSES converge at about the same time
Term
What is synaptic plasticity?
Definition
ability of some component of a synapse to change (either 1. change in neurotransmitter release 2. change in receptor sensitivity 3. change in the number of receptors)
Term
What is sensory memory?
Definition
Very short term retention of sensory input. Information that is scanned, evaluated and acted upon. Lasts less than a second and is electrical in nature
Term
What is a short-term memory?
Definition
Last seconds to minutes and most likely is electrical in nature
Term
What is a long-term memory?
Definition
Lasts hours and as long as a lifetime. Synaptic in nature (i.e. synaptic plasticity). Results in long term potentiation that enhances the neurotransmitter release, enhances receptor sensitivity and increases the number of receptors
Term
What are the 2 types of long term memory and describe each?
Definition
1. declarative/explicit - retention of events, people, places, facts etc... stored in various parts of the cerebrum. 2. Procedural/implicit - development of skills. stored in cerebrum and cerebellum. conditioned reflexes (pavlovs dogs).
Term
Where are acetlycholine receptors located?
Definition
Throughout the CNS and PNS
Term
Are Acetylcholine receptors excitatory or inhibitory?
Definition
Both; it is dictated by the postsynaptic membrane
Term
What disease is associated wtih the loss of cholinergic (acetylcholine) receptors? How is it treated?
Definition
Alzheimers - this can be tre
Term
What are the 3 types of monoamine neurotransmitters?
Definition
1. dopamine 2. norepinephrine 3. serotonin/5-HT
Term
Is dopamine excitatory or inhibitory?
Definition
both
Term
Where is dopamine primarily used?
Definition
CNS
Term
What 4 things is dopamine used for?
Definition
Movement, attention, motivation and pleasure
Term
What is the result of high levels of dopamine being released?
Definition
linked to tourette's, schizophrenia and psychosis. One would treat with a dopamine receptor antagonist (phenothiazines)
Term
What is the result of low levels of dopamine being released and how would you treat for thes things?
Definition
Linked to depression (treat with reuptake inhibitors like wellbutrin). Linked to addictive behavior (like smoking) and you would treat with a reuptake inhibitor like zyban. Also linked to attention deficit disorder and you would treat with a reuptake inhibitor like ritalin.
Term
What happens if dopamin producing cells die and how is this treated?
Definition
Results in parkinson's disease and is traditionally treated with levodopa (l-dopa) which is a precursor to dopamine
Term
Is Norepinephrine excitatory or inhibitory?
Definition
both
Term
What is norepinephrine important for in the body?
Definition
affects mood and attention
Term
What happens if you have low levels of norepinephrine and how would you treat this?
Definition
low levels linked to attention deficit disorder and you would treat with a norepinephrine reuptake inhibitor like ritalin. Also linked to depression and you would treat with a norepinephrine reuptake inhibitor like wellbutrin.
Term
What is the effect of serotonin/5-HT?
Definition
this is the "feel good" neurotransmitter
Term
Where is serotonin/5-HT found; where is it used?
Definition
Used in the CNS
Term
What is serotonin/5-HT important for?
Definition
Regulating temperature, sleep, mood and appetite
Term
What are low levels of serotonin/5-HT linked to and how is it treated?
Definition
linked to depression and treated with a selective serotonin reuptake inhibitor (SSRI). Also may be linked to sudden infant death syndrome.
Term
What is the effect of the drug ecstasy (or E) on serotonin/5-HT?
Definition
Causes massive serotonin/5-HT secretion and inhibits serotonin reuptake. Long term use can stop natural serotonin production
Term
What are the 3 types of amino acid neurotransmitters?
Definition
1. glutamate 2. GABA and 3. Glycine
Term
Where is glutamate found/used in the body?
Definition
in the CNS
Term
Is glutamate excitatory or inhibitory?
Definition
it is the major excitatory hormone of the CNS
Term
What is glutamate important for in the body?
Definition
Thought to be involved in learning and memory
Term
What is the effect of high levels of glutamate in the body?
Definition
Thought to be involved in seizures and neural degeneration. Treated with drugs that block glutamate receptors
Term
What recreational drug blocks glutamate receptors and what is the effect?
Definition
PCP/angel dust will block glutamate receptors and cause hallucinations
Term
Where is GABA found/used in the body?
Definition
in the CNS
Term
Is it excitatory or inhibitory?
Definition
Major inhibitory neurotransmitter of the CNS
Term
Drugs that increase GABA are used to treat what?
Definition
Epileptic activity (GABAergic drugs)
Term
The death of GABA-producing cells results in what disease and how would you treat this?
Definition
Huntingtons's disease would be treated with GABAergic drugs
Term
Where is Glycine used/found in the body?
Definition
Found throughout the CNS
Term
Is it an inhibitory or excitatory neurotransmitter?
Definition
Inhibitory neurotransmitter of the CNS
Term
What are the 3 types of neuropeptide neurotransmitters?
Definition
1. endorphins 2. enkephalins and 3. substance P
Term
Where are the neuropeptide neurotransmitters found/used in the body?
Definition
Throughout the CNS and PNS
Term
Are the endorphins and enkephalins excitatory or inhibitory?
Definition
They are inhibitory
Term
with in the body?
Definition
regulation of pain
Term
What two major drugs act on endorphins and enkephalins receptors in the body?
Definition
Morphine and demerol
Term
What does nalaxone do?
Definition
Used to treat opiod overdoses in the body by countering depression of the CNS
Term
Is substance P excitatory or inhibitory?
Definition
Excitatory
Term
What physiological processes does substance P regulate in the body?
Definition
pain, anxiety, nausea and breathing
Term
What is the effect of inhibiting substance P in the body?
Definition
prevents nausea and reduces pain
Term
What are the two types of gaseous neurotransmitters?
Definition
Nitric oxide and carbon MONOxide (CO not CO2)
Term
Can gaseous neurotransmitters be stored?
Definition
No, they are produced as they are needed
Term
Where is nitric oxide found/used in the body?
Definition
Throughout the CNS and PNS
Term
Is nitric oxide excitatory or inhibitory?
Definition
Both
Term
What processes is nitric oxide involved in?
Definition
Memory specifically, but also plays a role in erection, blood vessel tone, and neurotransmitter release to name a few
Term
Where is Carbon MONOxide found/used in the body?
Definition
Throughout the CNS and PNS
Term
Is Carbon MONOxide neurotransmitter excitatory or inhibitory?
Definition
Both
Term
What is the function of Carbon MONOxide neurotransmitter?
Definition
similar in function to nitric oxide... It is also thought to be a co-neurotransmitter with nitric oxide.
Term
Which Neurotransmitters are used only in the CNS?
Definition
The amino acid neurotransmitters (glutamate, GABA and glycine), Dopamine and serotonin/5-HT. All other neurotramsmitters are used throughout the CNS and the PNS.
Term
Which neurotransmitters are only excitatory or inhibitory?
Definition
Excitatory - glutamate, substance P; Inhibitory - GABA, Glycine and teh endorphins and enkephalins. All others can be excitatory or inhibitory depending on the circumstances or the post-synaptic membrane.
Term
Which neurotransmitter is released at the neuromuscular junction?
Definition
Acetylcholine
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